Colossians 4:14:

Luke, the beloved physician, and Demas, greet you.

See also:

Is It a Sin to Go to the Doctor or Take Medicine?
Objection: God Wouldn’t Heal Paul’s Thorn in the Flesh
Objection: Paul Did Not Believe in Faith Healing Because He Had a Doctor (Luke) Accompany Him
Notes on Exodus 15:25-26